Metacarbonate-hosted Spinel On Baffin Island, Nunavut, Canada: Insights Into the Origin of Gem Spinel and Cobalt-Blue Spinel
Bibliographic record
Abstract
Research Article| March 01, 2019 Metacarbonate-hosted Spinel On Baffin Island, Nunavut, Canada: Insights Into the Origin of Gem Spinel and Cobalt-Blue Spinel Philippe M. Belley; Philippe M. Belley § Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia, Canada V6T 1Z4 § Corresponding author e-mail address: phil.belley@gmail.com Search for other works by this author on: GSW Google Scholar Lee A. Groat Lee A. Groat Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia, Canada V6T 1Z4 Search for other works by this author on: GSW Google Scholar Author and Article Information Philippe M. Belley § Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia, Canada V6T 1Z4 Lee A. Groat Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, 6339 Stores Road, Vancouver, British Columbia, Canada V6T 1Z4 § Corresponding author e-mail address: phil.belley@gmail.com Publisher: Mineralogical Association of Canada First Online: 26 Mar 2019 Online Issn: 1499-1276 Print Issn: 0008-4476 © 2019 Mineralogical Association of Canada The Canadian Mineralogist (2019) 57 (2): 147–200. https://doi.org/10.3749/canmin.1800060 Article history First Online: 26 Mar 2019 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Philippe M. Belley, Lee A. Groat; Metacarbonate-hosted Spinel On Baffin Island, Nunavut, Canada: Insights Into the Origin of Gem Spinel and Cobalt-Blue Spinel. The Canadian Mineralogist 2019;; 57 (2): 147–200. doi: https://doi.org/10.3749/canmin.1800060 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyThe Canadian Mineralogist Search Advanced Search Abstract Samples from 14 spinel occurrences in the Lake Harbour Group (LHG), Baffin Island, Nunavut, Canada, were studied using a combination of petrography, whole rock geochemistry, microprobe analysis, and, where possible, geochronology. Spinel at most occurrences is blue to violet and generally not of gem quality. Two spinel occurrences near Kimmirut contain vivid blue, cobalt-enriched (0.03–0.07 wt.% CoO) spinel. The spinel mostly occurs in metasedimentary (sensu stricto) rocks, with the exception of a few metasomatic occurrences. All spinel occurs in marble and calc-silicate/silicate-rich metacarbonate rocks. Minerals occurring with spinel as part of a stable assemblage include calcite, dolomite, phlogopite, pargasite, diopside, humite, forsterite, scapolite, anorthite, graphite, and pyrrhotite. The spinel formed under peak granulite facies metamorphic conditions.Metasedimentary (s.s.) spinel-bearing rocks in the LHG are interpreted to have the following protoliths: (1) impure dolomite-bearing and dolomitic limestone; (2) dolomitic marl; and (3) evaporitic magnesitic marl. Other significant gemstone occurrences in the LHG (sapphire and lapis lazuli) are interpreted to have similar protoliths. Factors that favor spinel genesis in Mg-bearing metacarbonates include: (1) a low abundance of Si relative to Al, which is a primary control on whether spinel forms in most calc-silicate rocks; (2) low K activity limiting the formation of phlogopite and thus leaving Al available for spinel formation; (3) low XCO2 in marbles; and (4) insufficient quantities of Mg or dolomite reactant in diopsidite limiting Al incorporation into phlogopite to form spinel.The spatial distribution of Co enrichment at the cobalt-blue spinel occurrences is indicative of highly localized enrichment. Cobalt and Ni are interpreted to have been enriched in the original sediment, or during diagenesis or low-grade metamorphism. Concentrations of Co (up to 29 μg/g) and Ni are anomalously high, while concentrations of Fe, Mn, V, Cr, and Cu are much lower than expected; this chemical signature speculatively could be caused by diagenetic processes prior to metamorphism.Pyrrhotite strongly partitions Fe relative to spinel, and therefore an abundance of sulfide is expected to improve the attractiveness (and commercial value) of spinel by decreasing the amount of Fe incorporated, thus preventing spinel from having an overly dark color. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.003 | 0.006 |
| Science and technology studies | 0.010 | 0.003 |
| Scholarly communication | 0.003 | 0.001 |
| Open science | 0.002 | 0.002 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.009 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".